Brad: In my experience , the answer is no, they actually improved.
Caveat: we are talking about 4150 flange carbs here.
Ours improved again after Wilson had everything and, could have been better according to Wilson but we are space limited for using a carb spacer, Wilson used all the room we had and its just under 5/8.
But moving from the Pro Systems 950 to the Twin gave better plug readings as well as power.
The guys i know of that are dynoing with them aren't reporting anything negative that I recall.
Mark is going to have more data there than I so I will be interested to hear what he has learned on that subject.

fwiw- we set up initial tuning on the dyno where there is no outside/in air turbulence.
We find our jet stagger bank to bank , initial bleed check etc.
Then we finish jetting / tuning at the track .
So far, right to left bank staggered jetting has been the norm with any carb/intake/ engine combo we have dynoed/tested and thats helped distribution/power quite a bit in some cases.
I have not tried staggering bleeds yet, but i'm gonna try it and see what happens- grin- i just gotta see what i can do on fine tuning . Might be a really bad idea too!